Martin Franzel walked away from his Minneapolis home in 1963 and never returned. Aaron Anderson, 2, was last seen in his Pine City yard in 1989. This May, Cody Christle, 20, set off on foot from a friend’s Hinckley home and vanished.

These are three of the 147 Minnesotans in the National Missing and Unidentified Persons System (NamUs), the first publicly accessible nationwide database designed to solve some of the most puzzling and agonizing modern mysteries.

It has only been five years since the database became fully operational. That’s surprising, given that the agency behind NamUs, the U.S. Department of Justice, has overseen the National Crime Information Center since it debuted 47 years ago. That massive database also includes information on missing persons and unidentified bodies, but it remains a tool of law enforcement that is off-limits to the public.

The true power of NamUs is harnessing the collective knowledge of family, friends and other interested individuals to match unidentified remains with the names of vanished individuals. Public users can add their own missing persons cases onto the list, correct errors, provide additional information and, in many ways, do their own investigation, long after the case has gone cold.

Todd Matthews can attest to the detective ability of regular folks. Matthews was a factory worker in Tennessee when he became obsessed with learning the identity of a young woman found dead and wrapped in green canvas by the side of a Kentucky road in 1968. She was known only as “Tent Girl,” the name etched in her tombstone.

Matthews learned of the mystery 20 years later from the man who discovered Tent Girl (he would later become Matthews’ father-in-law). He started researching the case compulsively and when the Internet became widespread in the early 1990s, Matthews recognized its investigative potential immediately. In 1998, he came across a post by a woman looking for her missing sister, and he saw enough similarities that he contacted her.

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A sample of the Minnesota missing Blog post

The body was exhumed, DNA was matched and Tent Girl acquired a name: Barbara Ann Hackman-Taylor. While the circumstances of her death will never be known, her family could move on with their lives.

Tent Girl also changed Matthews’ life. He had found his true calling, and is now director of communications and quality assurance for NamUs.

“The public really appreciates it, because it’s something they have access to,” he said.

NamUs operates on a $3.5 million budget and works hand in hand with law enforcement, medical examiners and organizations like the National Center for Missing and Exploited Children. It employs data analysts, forensic dentists and fingerprint experts, and can arrange for DNA samples to be taken from family members.

Two-thirds of NamUs users are members of the public, and Matthews said they are the main reason the database has grown to 17,000 missing persons and 11,000 unidentified bodies. Some of the photos show bright, smiling faces. Others are unfocused and grainy, the images of people who disappeared long ago or whose connections to society were already so thin that few photos were ever taken. Each face brings to mind the circles of grief in the families and friends left behind.

Data from NamUs has so far helped clear up 737 missing persons cases. A description of a unicorn and rose tattoo on an unidentified body found in Ohio in August 1987 enabled a user of NamUs in 2009 to realize that it belonged to her missing sister. A hunter who discovered a partly buried vehicle in the Arizona wilderness in 2010 used the website to learn that it belonged to a man reported missing more than a year earlier. His remains were found nearby. In 2011, an inquiry by a law enforcement officer made a match between a man who walked away from a foster care home in Detroit in 1991 with a body found in Lake Erie the following spring.

These are the typical outcomes of cold cases. Probably the rarest is the “live recovery.”

By the mid-2000s, Theresa Rossi had not heard from her brother Leonard Bariana for more than a decade. They had grown up together in Philadelphia, but in his 20s, Bariana began his lifelong struggle with mental illness. He moved between family members in Philadelphia and New Jersey, and went in and out of mental hospitals. At some point he announced he was on his way to Naples.

His family thought he was talking nonsense, as usual, but Bariana meant Naples, Fla., not Italy. A few years later, he called his brother from Florida. When his brother called him back, Bariana had already moved on again.

About a decade ago, Rossi said, the family went on an “all-out search” that led nowhere. She reported him missing, and his profile was added to NamUs. In February 2010, a group home manager in northern Minnesota saw a pitch for NamUs during an episode of the ABC series “The Forgotten.” She checked the website, saw Bariana’s profile and realized that it was the same guy who had lived in her group home.

Bariana was the first missing person in NamUs found alive. “To me, that was a miracle,” said Rossi, who lives in Laurel Springs, N.J. “We were looking, looking, looking for him, all the time.”

The staff at NamUs put Rossi and Bariana in contact, and the brother and sister were reunited over the telephone. Rossi wept when she remembered it. “He wanted to come back to Philly. ‘I’m going back to Philly,’ he said.”

Rossi and her husband made plans to fly to Minnesota to visit him. But Bariana was terminally ill with lung cancer, and died in a Duluth hospital two weeks after their conversation. He was buried in Philadelphia, next to his mother. “He came home,” Rossi said.

Contact James Eli Shiffer at james.shiffer@startribune.com or 612-673-4116. Read his blog at startribune.com/fulldisclosure.